Gyroharmonic emissions induced by energetic ions in the equatorial plasmasphere

Journal Article · Fri Jun 01 00:00:00 EDT 1979 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA084iA06p02597· OSTI ID:6129829

Curtis, S A; Wu, C S

The general problem of the excitation of ion gyroharmonic electrostatic and electromagnetic waves by energetic ions (E> or approx. =0.1 MeV) in a thermal plasma as observed in the earth's plasmasphere is considered. The thermal plasma is taken to be predominantly H/sup +/ with trace higher Z ion constituents of ionospheric origin such as He/sup +/ and O/sup +/. This plasma component has a Maxwellian distribution and supports the waves which may be excited by energetic ions with Z> or approx. =1. The energetic ions possess a power law distribution in energy with strong pitch angle anisotropy. Coupling of the free energy source of the energetic ions to the waves is obtained via the velocity dependence of the ion gyrofrequency ..cap omega../sub 0/. Owing to constraints imposed by free energy coupling, wave amplification, and ion cyclotron damping, the dominant growth rates are found for nearly perpendicularly propagating fast magnetosonic waves closely confined to the magnetic equator. Growth is restricted to frequencies immediately below the ion gyroharmonics by the resonance condition and implies line widths of approx.10 /sup 3/..cap omega../sub 0/. The fast magnetosonic waves are found to have a significant electromagnetic component which decreases with increasing gyroharmonic number. The polarization becomes almost entirely electrostatic where the fast magnetosonic and ion Bernstein branches merge above the lower hybrid frequency. When it is compared to observations of ion gyroharmonic emissions, the theory implies that there exist a significant number of charge states for Z> or approx. =2 MeV ions in the plasmasphere.

• Research Organization: Laboratory for Planetary Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771
• OSTI ID: 6129829
• Journal Information: J. Geophys. Res.; (United States), Vol. 84:A6
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
PLASMASPHERE
ELECTROMAGNETIC RADIATION
ION PLASMA WAVES
BOLTZMANN STATISTICS
DISTRIBUTION FUNCTIONS
GYROFREQUENCY
IONIC COMPOSITION
IONOSPHERE
MAGNETOACOUSTIC WAVES
POLARIZATION
EARTH ATMOSPHERE
HYDROMAGNETIC WAVES
ION WAVES
PLANETARY IONOSPHERES
PLASMA WAVES
RADIATIONS
640203* - Atmospheric Physics- Magnetospheric Phenomena- (-1987)